The modern trend in the design and implementation of hearing devices is focusing to a large extent on reducing the physical size of the hearing device. Miniaturization of hearing device components is becoming increasingly feasible with rapid technological advances in the fields of power supplies, sound processing electronics and micro-mechanics. The demand for smaller and less conspicuous hearing devices continues to increase as a larger portion of our population ages and faces hearing loss. Those who face hearing loss also encounter the accompanying desire to avoid the stigma and self consciousness associated with this condition. As a result, smaller hearing devices which are cosmetically less visible are increasingly sought after.
Hearing device technology has progressed rapidly in recent years. First generation hearing devices were primarily of the Behind-The-Ear (BTE) type, where an externally mounted device was connected by an acoustic tube to a molded shell placed within the ear. With the advancement of component miniaturization, modem hearing devices rarely use this Behind-The-Ear technique, focusing primarily on one of several forms of an In-The-Canal hearing device. Three main types of In-The-Canal hearing devices are routinely offered by audiologists and physicians. In-The-Ear (ITE) devices rest primarily in the concha of the ear and have the disadvantages of being fairly conspicuous to a bystander and relatively bulky to wear. Smaller In-The-Canal (ITC) devices fit partially in the concha and partially in the ear canal and are less visible but still leave a substantial portion of the hearing device exposed. Recently, Completely-In-The-Canal (CIC) hearing devices have come into greater use. As the name implicates, these devices fit deep within the ear canal and are essentially hidden from view from the outside.
In addition to the obvious cosmetic advantages these types of in-the-canal devices provide, they also have several performance advantages that larger, externally mounted devices do not offer. Placing the hearing device deep within the ear canal and proximate to the tympanic membrane (ear drum) improves the frequency response of the device, reduces distortion due to jaw extrusion, reduces the occurrence of the occlusion effect and improves overall sound fidelity.
The anatomy of the ear canal includes ceruminous glands which secrete a yellowish, wax-like substance called cerumen (ear wax). Cerumen tends to accumulate in the ear canal. Due to both the action of cilia located within the ear canal and the natural movements of the ear canal, the cerumen gradually propagates outward. When a hearing device is inserted into the ear canal, it is susceptible to the effects of cerumen accumulation. Cerumen can often mix with sloughed off skin and dirt, further impairing operation of the hearing device.
With the onset of smaller and more sophisticated hearing devices, the buildup of cerumen can have more severe effects on their performance. Receivers (i.e., an acoustic speaker) utilized in most modern hearing devices are particularly susceptible to performance problems and damage from cerumen accumulation. Initially, cerumen accumulation physically blocks the receiver port occluding the acoustic path and preventing sound waves from efficiently reaching the tympanic membrane. Eventually, the cerumen can penetrate into the receiver housing and damage the sensitive mechanical and electrical components located within the housing. Most of these internal components are critical to the operation of the hearing device and their failure will necessitate repair or replacement of the hearing device. The monetary and time costs associated with replacing failed hearing devices due to cerumen clogging and receiver damage is significant.
U.S. Pat. No. 5,401,920, entitled "Cerumen Filter For Hearing Aids" ("the '920 patent"), discloses a replaceable and disposable wax guard that is affixed over the sound port of an in-the-ear hearing aid by means of a pressure sensitive tape. The filter itself is porous to sounds but is receptive to cerumen. While providing some level of protection against cerumen damage to the internal components of the hearing device, this and other similar types of "filters" become quickly soiled, resulting in poor device performance due to a blocked receiver port. As such, the disposable filter must be frequently replaced by the user. The small size of these devices often requires a high level of visual acuity and dexterity for such maintenance.
U.S. Pat. No. 5,327,500, entitled "Cerumen Barrier for Custom In The Ear Type Hearing Instruments" ("the '500 patent"), discloses a cerumen barrier for a custom, in the ear type hearing instrument. The cerumen barrier consists of a small door covering the receiver port which can be manually rotated open to provide cleaning under the door and around the receiver port. While also providing some level of protection against cerumen to the internal components of the hearing device, the '500 patent also requires significant user intervention to clean the filter.
Various other devices, and particularly those described in U.S. Pat. No. 4,879,750, entitled "Hearing Aid With Cerumen Trapping Gap," U.S. Pat. No. 5,105,904, entitled "Cerumen Trap For Hearing Aid," and U.S. Pat. No. 5,166,659, entitled "Hearing Aid With Cerumen Collection Cavity," utilize various types of trapping mechanisms to collect cerumen. However, in each of these devices the cerumen is simply collected and a user must still manually clear it from the device.